I've always wanted to make a list myself as well.. maybe one day i'll be bored enough to explore EVERY single map in the game and check...

hmm from checking your list I think I may have seen a box in a couple of these locations. i could be wrong. but one of use will have to check it out and make certain.

Egypt.. not sure where but I believe it was the pyramid. might even have one in the back of cairo where the hills are.
China defiantly has one where the sun quest is. (don't think I saw that on your list) another should be on the great wall or in that area or maybe its the buried city.
Osyla.. probably the arez quest area. (or I might be confusing that with the revival one)
Iceberg might have one.
South island one of the caves.. I think I might have came across one.. there is so many caves there so I can't be sure.. I could be wrong.

Gaahhhh I have 2 more places in my head but I can't remember now. if I do I'll add

Hmm I think later when I get more bluestone to make fuel I'll try and make it a mission to check each map. There was one time when I wanted to buy like 25-50 keys once when they were on sale and then go around the world and get a list of the boxes and what they had.. lol.. I would never do that now.. but I save the keys I get from eggs and perhaps one day I will have enough. Used to have some tradable keys.. .. lost them >.>